The invention relates to a method for bonding components such as hollow fan blade components and the like which eliminates certain steps so as to provide a more environmentally friendly method.
Fan blade components and the like are typically manufactured or machined in pieces which must then be assembled and bonded together. U.S. Pat. No. 5,063,662 discloses a method of forming a hollow blade, and describes the process for bonding components. Typically, such components are machined to provide desired shapes and contours, and must then be cleaned as disclosed in the aforesaid patent such that good bonding can result.
FIG. 1 also schematically illustrates a typical conventional process. As shown, after machining, components are conventionally treated in an anodizing step which places an oxide coating on surfaces of the components. This oxide coating is conventionally believed to interfere with obtaining a good bond, and the component is therefore processed with a series of steps to remove the oxide layer before bonding. Still referring to FIG. 1, after anodizing, the component is acid etched so as to highlight grains in the component, which assists in detecting any flaws. Following this acid etch, the component is washed using water, and inspected for defects. At this stage, the component still has an oxide coating from the anodizing step, and as shown in FIG. 1, the component is then subjected to a pickling step using an acid wash to backstrip or remove the oxide layer, followed by an alkali washing step to remove grease, oil and the like, and then a final wash using demineralized water so as to preserve the oxide-removed surface and provide the part with surfaces suitably prepared for bonding.
The method of FIG. 1, and also methods described in the ""662 patent, do provide a final bonded assembly having excellent bond quality, typically greater than 99%. However, the acid backstrip step results in a large quantity of environmentally hazardous and unfriendly materials which must be disposed of. Such acid streams also add to the overall cost of the process due to needs for special handling and disposal. Further, the need for demineralized water washing leads to additional waste materials, typically from sodium hydroxide or hydrochloric acid used to de-ionize the water for this step.
The need for environmentally friendly processes and techniques is well known, and it is clear that the need remains for a method for bonding components which reduces environmental impact while nevertheless providing a bonded assembly which is of sufficient quality.
It is therefore the primary object of the present invention to provide such a method.
It is a further object of the present invention to provide a method for bonding components which reduces costs of various processing steps.
Other objects and advantages of the present invention will appear hereinbelow.
In accordance with the present invention, a method is providing for bonding metal components, which method comprises the steps of providing metal components to be bonded together at contacting surfaces, said contacting surfaces having an oxide layer; washing said components with an alkali solution to provide alkali-washed components; washing said alkali-washed components with water to provide water-washed components; and bonding said components together at said surfaces.
In accordance with the present invention, the acid backstripping step conventionally believed to be necessary is avoided, and bonding is accomplished using oxide-coated surfaces, while nevertheless providing a bond which is of sufficient quality so as to readily exceed required levels.
This advantageously allows for the use of tap water rather than demineralized water in the final washing step, and reduces the amount of environmentally hazardous materials generated by the process.